Koi is a type of ceviche from Isaan in northern Thailand and Laos. I’ve also seen it described as a “raw larb“. The ingredients differ – beef, fish, snail, shrimp, sometimes even red ants – but it needs to be raw, and it’s prepared with lime juice and herbs and spices.
This recipe is very easy, put the tuna in a bowl and mix in hot chilies, cilantro, lemongrass, mint, onion, fish sauce, toasted rice powder, and a generous dose of lime juice. You don’t let it cure too long in the lime, though; the rawness of this dish is important. It’s really tasty, fresh and sharp and strong flavours all mixing together.
There have been some issues with the meat sources for koi in Isaan, with flukes that can cause liver cancer being found in the fish and snails that often go into this dish – so much so that liver cancer makes up 50% of cancers in the region. However, that’s more on the sourcing of the meat rather than the dish itself!